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Erbium filter in diagnostic radiology: calculations of contrast and patient mean ab­sorbed dose
Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.ORCID iD: 0000-0003-3352-8330
1989 (English)In: Optimisation of image quality and patient exposure: Proceedings of a Workshop organized jointly by the Commission of the European Communities and the Nationa lRadiological Protection Board / [ed] B. M. Moores, Β. F. Wall, Η. Eriskat and Η. Schibilla, London: British Institute of Radiology , 1989, 169-170 p.Conference paper, Published paper (Refereed)
Abstract [en]

Rare earth materials instead of aluminium as added filter have been reported to reduce the mean absorbed dose in the patient. With these filters, the energy spectrum can be shaped to yield high energy absorption in the detector (film or screen). Exchange of filter results in a change in contrast. The image contrast and the mean absorbed dose in the patient have been investigated in the case of detection of a small contrast detail in a homogeneous phantom. Image contrast is defined as the difference in optical densities on the film, behind and beside a small contrasting detail. The Monte Carlo photon transport technique has been used to calculate the mean absorbed dose in the phantom and the energy imparted to various intensifying screens. Different Xray spectra were obtained by varying tube potential and filter thickness as well as filter material. Using the image contrast as the image quality parameter, the optimization condition is to find that combination of tube potential, filter material and filter thickness that gives the lowest mean absorbed dose in the patient for a given contrast. The mean absorbed dose in a 2(H) mm thick water phantom is reduced by 1025% using an erbium filter at a tube potential which will give the same primary contrast as obtained with a 2 mm aluminium filter. Contrast equivalent tube potential, kVcq, is achieved at higher values than with a non ACcdgc filter like copper. With the same increase in tube load, the dose reduction using an erbium filter (130 mg/cm") is approximately as high as with a copper filter (200 mg/cm2). Dose reduction at equal contrast and filmblackening as with 2 mm aluminium added filter is higher at lower tube potentials. When the high atomic number of the detector material is at least ten below that of the filter, it is slightly favourable to dose reduction. The change in image contrast when exchanging the aluminium filter for one of erbium requires a change in tube potential to restore the contrast. This can be achieved with a decrease in patient mean absorbed dose at the expense of an approximate increase of two in tube load using 130 mg/cm" erbium as the added filter.

Place, publisher, year, edition, pages
London: British Institute of Radiology , 1989. 169-170 p.
Series
BIR Report, 20
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-20947ISBN: 0905749219 (print)OAI: oai:DiVA.org:liu-20947DiVA: diva2:236866
Conference
Workshop organized jointly by the Commission of the European Communities and the Nationa lRadiological Protection Board
Available from: 2009-09-25 Created: 2009-09-25 Last updated: 2017-02-09Bibliographically approved

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Sandborg, Michael

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